Tennis courts are relatively large. Tennis players and instructors are using ball retrievers and large number of tennis balls to minimize balls gathering time. Racquet Club's instructors utilize teaching carts which hold over three hundred tennis balls, ball machines carrying over two hundred tennis balls in one load and retrieving devises with over two hundred balls capacity to refill carts and ball machines. This equipment is efficient and convenient to use in Racquet Clubs, but bulky and unpopular for travelling with from site to site.
Portable metal wire baskets are used by instructors and tennis players practicing tennis on remote courts. Solid baskets with permanent handles and baskets with reversible handles are mostly used as portable devices for retrieving, collecting, dispensing tennis balls and for refilling ball machines.
Stap patented a basket with permanent handle in 1968, U.S. Pat. No. 3,371,950. He describes a tennis ball retriever and storage unit comprising an upright wire basket with a top dispensing opening, a handle mounted above the opening, a retrieving bottom grate including parallel rods spaced from each other a distance smaller than the tennis ball diameter, so as to define the space through which squeezed balls pushed against a tennis court flat surface enter and retain in the retriever. Retrieving method consists of placing the basket over a ball or a few balls, pushing it down and lifting the basket up with retrieved balls inside. Later pushed in through the bottom grate balls are moving previously retrieved balls up inside the basket. This sequence is repeated until the basket gets full.
A wire basket with permanent handle is easy to use and inexpensive to manufacture. It is light, relievable, does not require bending over during balls retrieving process and has small width and length. First balls portion retrieving procedure is effortless.
However, when considerable group of balls is collected in the basket with permanent handle, a push down force has to be raised. A compression of soft tennis balls is causing that need. Balls located at the basket bottom are deformed more then others by balls upper layers gravity and by side forces. Side forces appear as a result of an insertion retrieved balls in between balls resided at the basket bottom. Deformed balls internal pressure creates friction forces between balls inserted into the basket, between balls and basket walls. The coefficient of friction between tennis balls is relatively high, so distorted balls at the basket bottom grate are causing a significant resistance entering last balls into the basket. Commercially available the largest basket with permanent handle fits only eighty five balls. After retrieving balls a basket with permanent handle can be set on a tennis court surface for balls dispensing. A basket user has to stoop or to lift the basket for reaching tennis balls. A basket with permanent handle is inconvenient to use for dispensing purposes.
Seewagen and Markisz patented a basket with reversible handles in 1974, U.S. Pat. No. 3,820,836. They describe a tennis ball retrieval device with similar structure to the basket with permanent handle patented by Stap. This device retrieving bottom includes a yieldable under the pressure of the tennis ball flexible elements instantly returnable to normal position preventing the egress of the tennis ball from the receptacle. The device also comprises two reversible handles witch may have above the receptacle open top a carrying position or beneath the receptacle a supporting position.
Basket with reversible handles has all basket with permanent handle advantages plus balls dispensing procedure is convenient, because it may be placed above a tennis court surface on a suitable height for dispensing purposes. A user does not have to stoop or to lift basket for reaching tennis balls.
However, distorted balls at the basket bottom grate are causing a significant resistance for entering last balls into the basket with reversible handles also. Yieldable under the pressure of a tennis ball flexible elements reduce resistance for entering balls into the basket insignificantly. The largest commercially available wire basket with reversible handles fits one hundred forty balls and the most popular one fits only seventy five balls. Fully filled with balls wire baskets with reversible handles are relatively heavy to carry and to install in a dispensing position.
Madrazo patented a basket with reversible handles in 1995 U.S. Pat. No. 5,464,262. A ball retrieving and storage receptacle comprising a rectangular basket formed of pair of parallel tubular frame members connected together by parallel tubular members defining a bottom of the basket and spaces from each other by slightly less then the diameter of the ball. Basket has a top dispensing opening with a cover. Wheeled casters are provided along one side of the basket bottom. The bottom of a wheel of each caster has being disposed no lower than a plane passing through the bottom members of the frames. Basket includes a pair of U-shaped reversible handles. Each handle may pivot between first position above the basket and a second opposite position below the basket in which the basket is supported above a horizontal surface. When the basket is tilted onto the wheels of both casters, the basket may be pulled over a horizontal surface on the said wheels.
Madrazo's basket with reversible handles has an advantage in comparison with previously described devices. The filled with balls tilted basket with reversible handles is relatively easy to move around using casters.
But distorted balls at Madrazo's basket bottom are causing a significant resistance for entering last group of balls into a basket as well. In order to use casters, the basket has to be tilted to create a clearance between bottom frame and flat tennis court surface. When the basket is tilted, positioned above the basket reversible handles are leaning with the basket. User has to increase push down force to retrieve the last group of balls, because it's action line in not normal to a tennis court surface. In addition, filled Madrazo's basket is relatively heavy for setting up in a dispensing position.
Podejko patented a basket with reversible handles in 2002 U.S. Pat. No. 6,354,643. A tennis ball holder and retriever comprising swivel caster assemblies mounted to the corners of the basket with downwardly spring-based telescopic assemblies that position the basket above balls for a rolling movement.
Podejko's basket with reversible handles has all previously described devices advantages and, in addition, the fully filled with balls basket is relatively easy to move around without need of tilting.
On the other hand, distorted balls at the basket bottom grate are causing a significant resistance for entering last balls into the Podejko's basket also. Moreover, springs have to be stiff enough to keep the filled basket above a tennis court surface. It will require an additional push down force to overcome springs tension forces. Filled with balls Podejko's basket with reversible handles is relatively heavy to place in a dispensing position.
Racquet Club's instructors utilize rolling carts and rolling barrels as retrieving devices. These devices commonly utilize a handcart with ball retrieving mechanism and a rear handle. The user walks behind such a device and pushes it forward to retrieve and collect tennis balls. Some rolling carts and rolling barrels U.S. Pat. Nos. 4,077,533; 4,252,490; 4,318,654; 4,735,544; 3,902,749.
Rolling carts and rolling barrels are efficient devices. Most of them are capable to retrieve over two hundred balls at once.
However, they are larger, heavier, less reliable and more expensive then portable wire baskets.